| Autor: |
D. Jia, William M. Yen, Richard S. Meltzer, Lizhu Lu |
| Rok vydání: |
2003 |
| Předmět: |
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| Zdroj: |
Journal of Luminescence. :333-337 |
| ISSN: |
0022-2313 |
| DOI: |
10.1016/s0022-2313(02)00523-9 |
| Popis: |
A two-step photoconductivity measurement in Gd 2 O 3 :Er 3+ is used to determine the location of the f 11 energy levels of Er 3+ with respect to the host bands of Gd 2 O 3 . Photoconductivity (PC) experiments were performed with both a tunable UV source and with 488 nm Ar + excitation, as well as in the presence of both light sources. Using only the UV source, PC features with onsets at 240 and 340 nm are identified as direct band gap excitation and two-step excitation involving excited state absorption on Er 3+ respectively; the latter is confirmed by its quadratic dependence on intensity. Under simultaneous Ar + excitation, which enhances the population of the metastable 4 S3/2 Er 3+ excited state population, the PC feature with a 340 nm onset increases dramatically and its magnitude depends linearly on both UV and Ar + laser intensity, supporting its interpretation as resulting from excited state absorption form the 4 S 3/ 2 metastable Er 3+ excited state. The 340 nm onset of the signal allows one to place the 4 I 15/2 ground state at 0. 7±0.2eV below the top of the valence band. The lowest 4f 10 5d level then lies close to the bottom of the conduction band and its overlap with the conduction band is thought to enhance the second step in the photoionization process. |
| Databáze: |
OpenAIRE |
| Externí odkaz: |
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Full Text from ScienceDirect